"Exploring the Design Space of Graphical Passwords on Smartphones"の紹介

Bring Your Own Device (BYOD) is a growing trend among enterprises, aiming to improve workers' mobility and productivity via their smartphones. The threats and dangers posed by the smartphones to the enterprise are also ever-growing. Such dangers can be mitigated by running the enterprise software inside a "secure container" on the smartphone. In our work we present a systematic assessment of security critical areas in design and implementation of a secure container for Android using reverse engineering and attacker-inspired methods. We do this through a case-study of Samsung KNOX, a real-world product deployed on millions of devices. Our research shows how KNOX security features work behind the scenes and lets us compare the vendor's public security claims against reality. Along the way we identified several design weaknesses and a few vulnerabilities that were disclosed to Samsung.

Secure Containers in Android: the Samsung KNOX Case Study

User accounts at Internet services contain a multitude of personal data such as messages, documents, pictures, and payment information Passwords are used to protect these data from unauthorized access User authentication based on passwords has many advantages for both users and service providers Users can use passwords across many platforms, devices, and applications and do not need to carry an additional device Service providers can implement password-based user authentication with little effort and operate it with low cost per user

However, passwords have a key problem: the conflict between security and ease of use For security reasons, passwords must be attack-resistant, individual for each account, and changed on a regular basis But, these security requirements make passwords very difficult to use They require users to create and manage a large portfolio of passwords This poses three problems: First, the generation of attack-resistant passwords is very difficult Second, the memorization of many passwords is practically impossible Third, the regular change of passwords is very time-consuming These problems are aggravated by the different password requirements, interfaces, and procedures of services The preservation of passwords for users such as storing passwords on user devices mitigates the memorization problem, but it raises new problems: the confidentiality, availability, recoverability, and accessibility of the preserved passwords Despite decades of research, the problems of passwords are not solved yet Consequently, secure passwords are not usable in practice As a result, users select weak passwords, use them across accounts, and barely change them

In this thesis, we introduce the Password Assistance System (PAS) It makes secure passwords usable for users This is achieved by automation and comprehensive support PAS covers all aspects of passwords It generates, preserves, and changes passwords for users as well as ensures the confidentiality, availability, recoverability, and accessibility of the preserved passwords This reduces the efforts and activities of users to deal with passwords to a minimum and thus enables users to practically realize secure passwords for their online accounts for the first time

PAS is the first solution that is capable of handling the different password implementations of services This is achieved by a standardized description of password requirements, interfaces, and procedures Moreover, PAS is solely realized on the user-side and requires no changes on the service-side Both features ensure the practicability of PAS and make it ready to be used

PAS solves the password generation problem by creating attack-resistant, individual, and valid passwords for users automatically Users just need to provide the URL of a service to generate an optimal password for an account Our uniform description of password requirements provides the information to generate passwords in accordance with the individual password requirements of services PAS is able to generate the requirements descriptions automatically by extracting the password requirements of services from their websites So far, this was done for 185,696 services Moreover, PAS is equipped with an optimal password-composition rule set for the event that services do not explicitly state their password requirements, which is the usual case By means of the optimal rule set, PAS also generates attack-resistant passwords with the best possible acceptance rate in case of unknown password requirements

PAS solves the password memorization problem by preserving passwords for users This releases users from memorizing their passwords and facilitates to use individual passwords for accounts PAS makes users' password portfolios available on all their devices as well as automatically synchronizes changes PAS achieves this without storing passwords at servers so that an attacker cannot steal them from servers Moreover, PAS provides a backup solution to recover the preserved passwords in case of loss Users need to create backups only once and do not have to update them even when their password portfolios change Consequently, users can keep backups completely offline at secure, different, and physically isolated locations This minimizes the risk of compromise and loss as well as enables an emergency access to the passwords for trusted persons Moreover, PAS has a built-in revocation mechanism It allows users to completely invalidate devices and backups in case they lose control over them This guarantees that no passwords can be stolen from lost user devices and backups once revoked Users always have full control of their passwords

PAS solves the password change problem by changing passwords automatically for users Users neither need to create new passwords nor manually log in to their accounts Our uniform description of password interfaces and procedures provides the information to change passwords at arbitrary services Moreover, PAS is the first solution that provides autonomous password changes It changes passwords on a regular basis with respect to the security level of passwords as well as immediately after PAS detects a compromise of users' passwords

The practicability of PAS is demonstrated by an implementation The individual components of PAS can be used independently, integrated into other applications, and combined to a single user application, called a password assistant

In summary, this thesis presents a solution that makes secure passwords usable This is done by automation and comprehensive support in the generation and management of passwords

Generating and Managing Secure Passwords for Online Accounts

It is practically impossible for users to memorize a large portfolio of strong and individual passwords for their online accounts. A solution is to generate passwords randomly and store them. Yet, storing passwords instead of memorizing them bears the risk of loss, e.g., in situations where the device on which the passwords are stored is damaged, lost, or stolen. This makes the creation of backups of the passwords indispensable. However, placing such backups at secure locations to protect them as well from loss and unauthorized access and keeping them up-to-date at the same time is an unsolved problem in practice. 
We present PASCO, a backup solution for passwords that solves this challenge. PASCO backups need not to be updated, even when the user's password portfolio is changed. PASCO backups can be revoked without having physical access to them. This prevents password leakage, even when a user loses control over a backup. Additionally, we show how to extend PASCO to enable a fully controllable emergency access. It allows a user to give someone else access to his passwords in urgent situations. We also present a security evaluation and an implementation of PASCO.

Update-tolerant and Revocable Password Backup (Extended Version).

It is practically impossible for users to memorize a large portfolio of strong and individual passwords for their online accounts. A solution is to generate passwords randomly and store them. Yet, storing passwords instead of memorizing them bears the risk of loss, e.g., in situations where the device on which the passwords are stored is damaged, lost, or stolen. This makes the creation of backups of the passwords indispensable. However, placing such backups at secure locations to protect them as well from loss and unauthorized access and keeping them up-to-date at the same time is an unsolved problem in practice.

Update-Tolerant and Revocable Password Backup

Many systems rely on passwords for authentication. Due to numerous accounts for different services, users have to choose and remember a significant number of passwords. Password-Manager applications address this issue by storing the user's passwords. They are especially useful on mobile devices, because of the ubiquitous access to the account passwords.

Mattias Rauter

Papers

Do you think your passwords are secure